block/export: Allocate BlockExport in blk_exp_add()

Instead of letting the driver allocate and return the BlockExport
object, allocate it already in blk_exp_add() and pass it. This allows us
to initialise the generic part before calling into the driver so that
the driver can just use these values instead of having to parse the
options a second time.

For symmetry, move freeing the BlockExport to blk_exp_unref().

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-17-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 14 insertions, 12 deletions

diff --git a/blockdev-nbd.c b/blockdev-nbd.c
index ef14303b25..b34f159888 100644
--- a/blockdev-nbd.c
+++ b/blockdev-nbd.c
@@ -173,18 +173,19 @@ void qmp_nbd_server_start(SocketAddressLegacy *addr,
     qapi_free_SocketAddress(addr_flat);
 }
 
-BlockExport *nbd_export_create(BlockExportOptions *exp_args, Error **errp)
+int nbd_export_create(BlockExport *exp, BlockExportOptions *exp_args,
+                      Error **errp)
 {
     BlockExportOptionsNbd *arg = &exp_args->u.nbd;
     BlockDriverState *bs = NULL;
-    NBDExport *exp = NULL;
     AioContext *aio_context;
+    int ret;
 
     assert(exp_args->type == BLOCK_EXPORT_TYPE_NBD);
 
     if (!nbd_server && !is_qemu_nbd) {
         error_setg(errp, "NBD server not running");
-        return NULL;
+        return -EINVAL;
     }
 
     if (!arg->has_name) {
@@ -193,22 +194,22 @@ BlockExport *nbd_export_create(BlockExportOptions *exp_args, Error **errp)
 
     if (strlen(arg->name) > NBD_MAX_STRING_SIZE) {
         error_setg(errp, "export name '%s' too long", arg->name);
-        return NULL;
+        return -EINVAL;
     }
 
     if (arg->description && strlen(arg->description) > NBD_MAX_STRING_SIZE) {
         error_setg(errp, "description '%s' too long", arg->description);
-        return NULL;
+        return -EINVAL;
     }
 
     if (nbd_export_find(arg->name)) {
         error_setg(errp, "NBD server already has export named '%s'", arg->name);
-        return NULL;
+        return -EEXIST;
     }
 
     bs = bdrv_lookup_bs(NULL, exp_args->node_name, errp);
     if (!bs) {
-        return NULL;
+        return -ENOENT;
     }
 
     aio_context = bdrv_get_aio_context(bs);
@@ -218,6 +219,7 @@ BlockExport *nbd_export_create(BlockExportOptions *exp_args, Error **errp)
         arg->writable = false;
     }
     if (bdrv_is_read_only(bs) && arg->writable) {
+        ret = -EINVAL;
         error_setg(errp, "Cannot export read-only node as writable");
         goto out;
     }
@@ -226,22 +228,22 @@ BlockExport *nbd_export_create(BlockExportOptions *exp_args, Error **errp)
         exp_args->writethrough = false;
     }
 
-    exp = nbd_export_new(bs, arg->name, arg->description, arg->bitmap,
+    ret = nbd_export_new(exp, bs, arg->name, arg->description, arg->bitmap,
                          !arg->writable, !arg->writable,
                          exp_args->writethrough, errp);
-    if (!exp) {
+    if (ret < 0) {
         goto out;
     }
 
     /* The list of named exports has a strong reference to this export now and
      * our only way of accessing it is through nbd_export_find(), so we can drop
      * the strong reference that is @exp. */
-    blk_exp_unref((BlockExport*) exp);
+    blk_exp_unref(exp);
 
+    ret = 0;
  out:
     aio_context_release(aio_context);
-    /* TODO Remove the cast: nbd_export_new() will return a BlockExport. */
-    return (BlockExport*) exp;
+    return ret;
 }
 
 void qmp_nbd_server_add(NbdServerAddOptions *arg, Error **errp)